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Researchers pursue invisibility cloak upgrade by printing

Duke researchers are using a new method in their efforts to develop more advanced invisibility cloaking devices.

Funded by the Army Research Office, researchers at the Center for Metamaterials and Integrated Plasmonics have continued their research in cloaking technologies— devices that bend electromagnetic waves around an object so that it appears undetectable in a single plane. Led by Yaroslav Urzhumov, assistant research professor of electrical and computer engineering,  the research team strayed away from the previous approach of using advanced metamaterials and precise measurements. Instead, they are using algorithms to optimize invisibility using simple three-dimensional printed materials.

“I am more hopeful than ever that our research in electromagnetic metamaterials is going to lead to practical applications, and even commercially available devices for non-military applications,” Urzhumov said.

The researchers’ current strategy—three-dimensional printing technology—uses numerically based guidelines to create the best model for invisibility using simple polymers. The alternative approach of metamaterials involves highly accurate measurements of man-made compounds that exhibit properties not found in nature.

“There are different competing cloaking technologies right now,” said Nathan Landy, a graduate student in electrical and computer engineering.

Both approaches are currently restricted in cloaking objects in only one plane. Although current cloaking devices do not make objects disappear in visible light, Urzhumov explained that technologies to make objects invisible to the human eye will likely use different technologies.

“There’s a big difference between creating illusions for human eyes and completely hiding an object from any kind of radiation sensor,” said Urzhumov, noting that the human eye only uses three colors to form images and has a minimum movement frequency of 25 frames per second.

Cloaking device research and radar systems currently use different portions of the microwave spectrum of electromagnetic waves. Research on cloaking devices utilizes the X-Band of the spectrum defined by a frequency of ten gigahertz. Current radar systems, however, utilize the K-Band, which has waves that have a frequency of 24 GHz. Urzhmov explained that invisibility research aims to increase the frequencies that the devices are able to practically cloak objects to hide them from radars.

There are many technologies that the lab is working on that hope to improve and expand the cloaking devices the lab has previously produced, Urzhumov said.

“What we made is a two-dimensional device, which means that it only have this cloaking effect when it’s illuminated at an appropriate angle,” Urzhumov said. Researchers hope to move past the 2D restriction and go into three dimensional cloaking technologies, something that Urzhomov thinks is more possible with sophisticated 3D printing technologies.

Urzhumov also hopes to make the technology applicable to larger objects. For example, by connecting separate polymer pieces to cloak a human head. 

“We are just scratching the surface, and the cloaks are just the tip of the 3D-printing iceberg,” said Urzhumov.

Those outside academia can also appreciate the challenge to current technological limitations.

“The research is really exciting, not only because Harry Potter fans are one step closer to having their dreams fulfilled,” sophomore James Sawyer said. “It really lets you realize what’s possible with new technologies readily available at our fingertips."


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